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[34.125.73.210]) by smtp.gmail.com with ESMTPSA id q6-20020a170902a3c600b001dd0d0d26a4sm3384097plb.147.2024.04.12.11.41.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 12 Apr 2024 11:41:15 -0700 (PDT) Date: Fri, 12 Apr 2024 11:41:11 -0700 From: David Matlack To: James Houghton Cc: Andrew Morton , Paolo Bonzini , Yu Zhao , Marc Zyngier , Oliver Upton , Sean Christopherson , Jonathan Corbet , James Morse , Suzuki K Poulose , Zenghui Yu , Catalin Marinas , Will Deacon , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Shaoqin Huang , Gavin Shan , Ricardo Koller , Raghavendra Rao Ananta , Ryan Roberts , David Rientjes , Axel Rasmussen , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, kvm@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org Subject: Re: [PATCH v3 0/7] mm/kvm: Improve parallelism for access bit harvesting Message-ID: References: <20240401232946.1837665-1-jthoughton@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240401232946.1837665-1-jthoughton@google.com> X-Rspamd-Queue-Id: CE15B40007 X-Rspam-User: X-Stat-Signature: ch1t1h9f515asq1i16kdq9exhhezohbx X-Rspamd-Server: rspam03 X-HE-Tag: 1712947277-268102 X-HE-Meta: U2FsdGVkX183sCi1aStrcJbeqazCx8omUA7DKLHP7ZO1KjulOdq+Ei3z9dLD4A8wVCvL3uehpmjNZ+ImCm2LtpqrPvf1FaLijDmtmhA9mXZeouwQpXat+eMRr4mWlE8xCxJzrsFY/N/EXnDogBY5kgX7bA23F/bdVWsimOFikRAXwt9xOkflK5MkXVaKX5lU0dU9znMq76NtZSRQfjPd+s1ajJ8YT/ox5/0d3pOVm7LTUxINJoXiPzOTEOlh3EDWdkIwzM+B8v4Z6JBIhuZIUfEUNkBdsZLuPHlll2kJcHFThP3oytAvZFlt4ktmJP/RowogC/p+bQCTtqnMhWjfoWWKErnVt/u8Qo25RqlQGc/VY2RDw3VuHtEnGULa+gQVxnopLYaeNLTWQmp6CRNKJlfLZdWxG+PBG5MTppectgHXqSpx3Bl6rSKJ1WnZgErA3cUOD0v9VrPOZ65X6asYLjyWEbeABeGXWb45FiRta2dzH/ly03d03t+/uCirgt1WeHw0SdggK1sDzwFS56MmGcj8prBt3gzTJfpyKM7vSZmbIdGSfi+yrVGVG+qALYoqvyt8+VmejplVVOLXGmpOKHf2jSCdYUqsy1Y2pNP8FfEfjEOzzY1OKXKGSco/M315Q2Epy2KyPtS+HYjYjZYNkXivhkTd5q5lvImt5RgS0rgG1WXhY1F105R4yajRWYdFkMPT59dLSl6YH4sBqv4JIo62DT2CtpfoH7KQj/vlvilLIJ/VK+rVuGBi13lSxmb2VoaKozugnaNAC2ZI4iPU+UX9LaJwIW9HBzXIPcbIlxSDLGkipBeMUw9yJPEXuJipmBjPYI+6fPt3WnkMhAqQZyRzWK1htEn0YFazxCXUrwmZuRgRApAWiHaSt6UknHV1AnffTUF15pEonLAZEH2RPpxjT4tjUAn9Qto84du74PoOVfETgVenmSpKRVUnhFpxJP00ToscvFtPEV/gel2 pvYwHYoc ou/wuUVNonz7x2sMOcyBZDfjoXiSD4H2lO39U2Cqiv7iDjHBT+CdfQuG/WhSe5LGnA43/7IVbWrbjezxbF1b51ElhJoxeydLMFTkhW8GXqu8gar2xdUP+y7rJSNNkKVaW/14gqzLwz/ttAFYawhMqCecOTMM7iCuCLUV4ckTaThQ1C1uaqe5LuK3Dsa2miW4U+4zGB9A4rgsb1s1CXuAjn0MEhjJZw/YpFYDk6F72dxPFG8ypaGsiRjvIBHw5Az6yG33zFPIpebKEEkpWtN2EmB2fo5Lbk+9Tbj7NWm7gDCwZy56+e0LirllyhdMmLIyANajmNisrKU+dMza7nWhArcL1UNSq0JJn9m/gsJcszYMYxjo4NXQP9wbSDH9jTT/NduFJp2+6vPh/DfzZTZ0Tb7L00g== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2024-04-01 11:29 PM, James Houghton wrote: > This patchset adds a fast path in KVM to test and clear access bits on > sptes without taking the mmu_lock. It also adds support for using a > bitmap to (1) test the access bits for many sptes in a single call to > mmu_notifier_test_young, and to (2) clear the access bits for many ptes > in a single call to mmu_notifier_clear_young. How much improvement would we get if we _just_ made test/clear_young lockless on x86 and hold the read-lock on arm64? And then how much benefit does the bitmap look-around add on top of that?